The present invention relates a liquid crystal display device useful for a liquid crystal projector which illuminates a liquid crystal display element with light from a light source and projects images on the liquid crystal display element on a screen.
Recently, liquid crystal display devices have been widely used in small-sized display devices, display terminals for office automation equipment and the like. Basically, a liquid crystal display device includes a liquid crystal display panel (also called a liquid crystal display element or a liquid crystal cell) composed of a pair of insulating substrates at least one of which is made of a transparent plate, a transparent plastic plate or the like, and a layer of liquid crystal composition (a liquid crystal layer) sandwiched between the insulating substrates.
The liquid crystal display devices are divided roughly into the simple-matrix type and the active matrix type. In the simple-matrix type liquid crystal display device, a picture element (hereinafter a pixel) is formed by selectively applying voltages to pixel-forming strip electrodes formed on both of the two insulating substrates of the liquid crystal display panel, and thereby changing orientation of a portion of liquid crystal molecules of the liquid crystal composition corresponding to the pixel. On the other hand, in the active-matrix type liquid crystal display device, the liquid crystal display panel is provided with signal lines, pixel electrodes, reference voltage electrodes and active elements each associated with one of the pixel electrodes for pixel selection which are formed on one of the substrates, and a pixel is formed by selecting the active element associated with the pixel and thereby changing orientation of liquid crystal molecules present between a pixel electrode connected to the active element and the reference voltage electrode associated with the pixel electrode.
Generally, the active matrix type liquid crystal display device employs the so-called vertical electric field type in which an electric field for changing orientation of liquid crystal molecules is applied between an electrode disposed on one of a pair of opposing substrate and another electrode disposed on the other of the opposing substrates. Also put to practical use is the so-called horizontal electric field type (also called IPS (In-Plane Switching) type) liquid crystal display device in which an electric field for changing orientation of liquid crystal molecules is applied in a direction approximately in parallel with the major surfaces of the opposing substrates.
Among display devices employing the liquid crystal display device, a liquid crystal projector has been practical use. The liquid crystal projector illuminates a liquid crystal display element with light from a light source and projects images on the liquid crystal display element on a screen. Two types, a reflective type and a transmissive type, of liquid crystal display elements are usable for liquid crystal projector. The reflective type liquid crystal display element is capable of being configured to make approximately the entire pixel area an useful reflective area, and consequently it has advantages of its small size, high definition display and high luminance over the transmissive type liquid crystal display element.
Consequently, a small-sized high-definition liquid crystal projector can be realized by using the reflective liquid crystal display element without decreasing its luminance.
A reflective liquid crystal display element is disclosed in U.S. Pat. No. 5,978,056 issued on Nov. 2, 1999, for example. U.S. Pat. No. 5,978,056 discloses a multilayer light blocking film, but does not disclose the arrangement of two light blocking films spaced from each other in a direction of their thickness.